Your midwife says you're 24 weeks, and your mom wants to know how many months that is. The first two charts you find online give her different answers.
Both charts can be right, because converting pregnancy weeks to months depends on how long you decide a month is. Below is a full chart from week 1 to 42 with its method shown, plus short answers for the weeks people ask about most. If you're not sure of your week, our due date calculator shows how many weeks and days pregnant you are.
Pregnancy is counted in weeks, about 40 from the first day of your last period (ACOG). Divide the days by about 30.4 to turn weeks into calendar months, which makes 40 weeks a little over 9 months.
Key Takeaways
- Your provider counts in weeks and days from the first day of your last period, and by convention your due date is 280 days (40 weeks) after it (ACOG, Committee Opinion 700, reaffirmed 2025).
- A calendar month averages 30.44 days, or about 4.35 weeks, so 40 weeks comes to about 9.2 months.
- The "4-week month" shortcut turns the same 40 weeks into 10 months, which is where "10 months pregnant" comes from.
- 36 weeks is about 8.3 calendar months: 8 months and 1 week, in your 9th month.
- Trimester lines depend on the source. ACOG ends the first trimester at 13 weeks and 6 days, and the NHS ends it at week 12.
Pregnancy Weeks to Months Chart
Each row is the first day of that week, so 28 means 28 weeks and 0 days since the first day of your last period. We multiply the weeks by 7, then divide by 30.44 days, the average calendar month (365.25 days divided by 12). The calendar months column shows whole months completed plus whole weeks left over, with the decimal in brackets. A month runs about 4.35 weeks, so some rows read "4 weeks" before the next month begins.
The last column divides the weeks by 4. ACOG, the NHS and MedlinePlus all measure pregnancy in weeks, and none of the pages we used defines "months pregnant," so every chart has to pick a method.
The chart needs your week. Enter your last period, conception date or IVF transfer in our due date calculator to see it.
Trimesters follow ACOG's definitions: the first runs to 13 weeks 6 days, the second from 14 weeks 0 days to 27 weeks 6 days, and the third from 28 weeks 0 days to 40 weeks 6 days. The NHS week-by-week guide puts week 13 in the second trimester, and our due date calculator follows that split.
First Trimester: Weeks 1 to 13 in Months
| Weeks | Calendar months | Month you're in | 4-week months |
|---|---|---|---|
| 1 | 0 months, 1 week (0.23) | 1st | 0.25 |
| 2 | 0 months, 2 weeks (0.46) | 1st | 0.5 |
| 3 | 0 months, 3 weeks (0.69) | 1st | 0.75 |
| 4 | 0 months, 4 weeks (0.92) | 1st | 1 |
| 5 | 1 month, 0 weeks (1.15) | 2nd | 1.25 |
| 6 | 1 month, 1 week (1.38) | 2nd | 1.5 |
| 7 | 1 month, 2 weeks (1.61) | 2nd | 1.75 |
| 8 | 1 month, 3 weeks (1.84) | 2nd | 2 |
| 9 | 2 months, 0 weeks (2.07) | 3rd | 2.25 |
| 10 | 2 months, 1 week (2.30) | 3rd | 2.5 |
| 11 | 2 months, 2 weeks (2.53) | 3rd | 2.75 |
| 12 | 2 months, 3 weeks (2.76) | 3rd | 3 |
| 13 | 2 months, 4 weeks (2.99) | 3rd | 3.25 |
Weeks 1 and 2 come before you're pregnant: ACOG explains that pregnancy is assumed to start 2 weeks after the first day of your last period. Our first trimester guide covers this stage.
Second Trimester: Weeks 14 to 27 in Months
| Weeks | Calendar months | Month you're in | 4-week months |
|---|---|---|---|
| 14 | 3 months, 0 weeks (3.22) | 4th | 3.5 |
| 15 | 3 months, 1 week (3.45) | 4th | 3.75 |
| 16 | 3 months, 2 weeks (3.68) | 4th | 4 |
| 17 | 3 months, 3 weeks (3.91) | 4th | 4.25 |
| 18 | 4 months, 0 weeks (4.14) | 5th | 4.5 |
| 19 | 4 months, 1 week (4.37) | 5th | 4.75 |
| 20 | 4 months, 2 weeks (4.60) | 5th | 5 |
| 21 | 4 months, 3 weeks (4.83) | 5th | 5.25 |
| 22 | 5 months, 0 weeks (5.06) | 6th | 5.5 |
| 23 | 5 months, 1 week (5.29) | 6th | 5.75 |
| 24 | 5 months, 2 weeks (5.52) | 6th | 6 |
| 25 | 5 months, 3 weeks (5.75) | 6th | 6.25 |
| 26 | 5 months, 4 weeks (5.98) | 6th | 6.5 |
| 27 | 6 months, 0 weeks (6.21) | 7th | 6.75 |
Back to that 24-week appointment: by calendar months you're about 5.5 months along and in your 6th month, while the 4-week shortcut says an even 6. Our second trimester guide walks through these weeks.
Third Trimester: Weeks 28 to 42 in Months
| Weeks | Calendar months | Month you're in | 4-week months |
|---|---|---|---|
| 28 | 6 months, 1 week (6.44) | 7th | 7 |
| 29 | 6 months, 2 weeks (6.67) | 7th | 7.25 |
| 30 | 6 months, 3 weeks (6.90) | 7th | 7.5 |
| 31 | 7 months, 0 weeks (7.13) | 8th | 7.75 |
| 32 | 7 months, 1 week (7.36) | 8th | 8 |
| 33 | 7 months, 2 weeks (7.59) | 8th | 8.25 |
| 34 | 7 months, 3 weeks (7.82) | 8th | 8.5 |
| 35 | 8 months, 0 weeks (8.05) | 9th | 8.75 |
| 36 | 8 months, 1 week (8.28) | 9th | 9 |
| 37 | 8 months, 2 weeks (8.51) | 9th | 9.25 |
| 38 | 8 months, 3 weeks (8.74) | 9th | 9.5 |
| 39 | 8 months, 4 weeks (8.97) | 9th | 9.75 |
| 40 | 9 months, 0 weeks (9.20) | 10th | 10 |
| 41 | 9 months, 1 week (9.43) | 10th | 10.25 |
| 42 | 9 months, 2 weeks (9.66) | 10th | 10.5 |
ACOG's third trimester ends at 40 weeks 6 days, so weeks 41 and 42 run past it. The NHS guide continues to week 41.
How Many Months Pregnant at 28, 29, 32, 36 and 40 Weeks?
Each answer uses the chart's method and links to that week in our pregnancy week by week series.
How Many Months Is 28 Weeks Pregnant?
At 28 weeks you're 196 days along, about 6.4 calendar months: 6 months and 1 week, in your 7th month. The 4-week shortcut makes it an even 7. ACOG and the NHS both start the third trimester here; see our 28 weeks pregnant guide.
How Many Months Is 29 Weeks Pregnant?
Twenty-nine weeks is 203 days, about 6.7 calendar months: 6 months and 2 weeks, still your 7th month. The 4-week shortcut says 7.25. More in our 29 weeks pregnant guide.
How Many Months Is 32 Weeks Pregnant?
At 32 weeks you're 224 days along, about 7.4 calendar months: 7 months and 1 week, in your 8th month. The 4-week shortcut gives an even 8, which is why many charts call it "8 months pregnant." See our 32 weeks pregnant guide.
How Many Months Is 36 Weeks Pregnant?
Thirty-six weeks is 252 days, about 8.3 calendar months: 8 months and 1 week, in your 9th month. The 4-week shortcut makes it an even 9, so "about 8 months" and "9 months" both get said for the same week. See our 36 weeks pregnant guide.
How Many Months Is 40 Weeks Pregnant?
Forty weeks is 280 days, about 9.2 calendar months: 9 months and about 6 days, which puts you in the first days of your 10th month. The 4-week shortcut makes it an even 10. Forty weeks is your estimated due date; our 40 weeks pregnant guide covers what happens around it.
How Many Weeks Is 3, 8 or 9 Months Pregnant?
To go the other way, multiply the months by 30.44 and divide by 7. Three calendar months come to about 91.3 days, so you pass 3 months at 13 weeks and 1 day. The 4-week shortcut says 12 weeks, the last week of the NHS first trimester.
How Many Weeks Is 8 Months Pregnant?
Eight calendar months come to about 243.5 days, or 34.8 weeks, so you pass 8 months at 34 weeks and 6 days. The 4-week shortcut says 32 weeks, which is why "8 months pregnant" can mean anything from 32 weeks to almost 35. Your 8th calendar month runs from 30 weeks 4 days to 34 weeks 5 days.
How Many Weeks Is 9 Months Pregnant?
Nine calendar months come to about 273.9 days, so you pass 9 months at 39 weeks and 1 day. The 4-week shortcut says 36 weeks. Your 9th calendar month runs from 34 weeks 6 days to 39 weeks 0 days, ending the week before a 40-week due date.
Is Pregnancy 9 or 10 Months?
Both, and the length of a month decides it. ACOG puts the due date 280 days after the first day of your last period, by convention. Divided by 30.44, that's about 9.2 calendar months; divided into 4-week blocks, it's an even 10.
| Way of counting | 40 weeks equals |
|---|---|
| Calendar months from your last period | About 9.2 months |
| 4-week months from your last period | 10 months |
| Calendar months from conception (38 weeks, or 266 days) | About 8.7 months |
ACOG says pregnancy is assumed to start 2 weeks after your last period began, so the first two weeks happen before you conceive. The 280-day convention has a history of its own: why your due date is 40 weeks (Naegele's rule).
How Long Is Pregnancy, Really?
ACOG's Committee Opinion 579, reaffirmed in 2025, says a single-baby pregnancy lasts an average of 40 weeks (280 days) from the first day of the last period to the estimated due date. Your own due date is an estimate built on that average.
Sources draw the normal range in different places. The NHS says pregnancy normally lasts 37 to 42 weeks from the first day of your last period, while MedlinePlus, from the U.S. National Library of Medicine, gives 38 to 42 weeks. In calendar months, 37 weeks is about 8.5, 38 weeks about 8.7 and 42 weeks about 9.7.
ACOG also names the weeks around your due date: 37 and 38 weeks are early term, and full term runs from 39 weeks 0 days to 40 weeks 6 days. ACOG's Committee Opinion 700 notes that the 280-day rule assumes a 28-day cycle with ovulation on day 14, and that a first-trimester ultrasound can improve the accuracy of the due date. If your date changed after a scan, ask your OB or midwife which week to go by.
Know your last period, conception date or IVF transfer date? The calculator gives your weeks and days, your trimester, and how many days are left until your estimated due date. Find your week in our due date calculator.
Frequently Asked Questions
How many months is 36 weeks pregnant?
About 8.3 calendar months: 8 months and 1 week, which puts you in your 9th month. Counted in 4-week months, 36 weeks is an even 9 months, so you will hear both answers.
How many months is 32 weeks pregnant?
About 7.4 calendar months: 7 months and 1 week, in your 8th month. Counted in 4-week months, 32 weeks is an even 8 months, which is why many charts call it 8 months pregnant.
How many months is 40 weeks pregnant?
About 9.2 calendar months, because 40 weeks is 280 days: 9 months and about 6 days, or 10 months if you count 4-week months. Forty weeks marks the estimated due date, and the NHS says pregnancy normally lasts 37 to 42 weeks.
How many weeks is 9 months pregnant?
Nine calendar months come to about 274 days, so you pass 9 months at 39 weeks and 1 day. Counted in 4-week months, 9 months is 36 weeks.
Is pregnancy 9 or 10 months?
Both, depending on the arithmetic. Counted in calendar months of about 30.4 days, the 40 weeks from your last period come to about 9.2 months. Counted in 4-week months, they come to an even 10.
Why do doctors count pregnancy in weeks, not months?
A week is always 7 days, while calendar months run 28 to 31 days. ACOG uses gestational age in weeks and days to time prenatal care and tests and to check that a baby is growing as expected.
This article is for information only and does not replace medical advice from your OB or midwife.
How This Guide Was Made
The Babysential Team wrote this guide from the sources below, checked on October 11, 2026, with AI-assisted drafting. Every figure was calculated with a script.
Sources
- Methods for Estimating the Due Date, Committee Opinion No. 700. ACOG, 2017, reaffirmed 2025
- How Your Fetus Grows During Pregnancy. ACOG, last reviewed 2026
- Definition of Term Pregnancy, Committee Opinion No. 579. ACOG, 2013, reaffirmed 2025
- Due date calculator. NHS, 2024
- Week-by-week guide to pregnancy. NHS Best Start in Life, 2025
- 4 weeks pregnant. NHS Best Start in Life, 2026
- Gestational age. MedlinePlus, U.S. National Library of Medicine, 2025
